Tuesday marks a difficult milestone for Amy Sue Pagnac's family and friends: the 25th anniversary of the 13-year-old's disappearance.

While police continue to investigate the Maple Grove cold case, there are few clues to where she went that August day in 1989 and where she is 25 years later.

"It's a very painful time of the year," said her sister, Susan Pagnac Jr., who was 8 when Amy disappeared. "The loss of all those years …"

For the past two months, attention on Amy's story and police work has ramped up, with FBI investigators, state forensic scientists and police officers searching the Pagnacs' house and digging up the back yard in May. In June, they dug up areas of the family's Isanti County farm. And this Saturday Amy will be among those that her Osseo classmates will honor at their 20-year high school reunion.

"We're always looking [for Amy]," said her sister. "And we still want anyone with information to come forward and go to talk to the police again."

Police say Amy, who would now be 38 years old, could be alive or dead. Last Saturday, Cpt. Keith Terlinden declined to say what prompted the two searches or whether anything was found, saying it could compromise the active investigation. But since attention on the case resurfaced in May, he said the two detectives assigned to the case have received a "fair amount" of tips.

"We're continuing to work with the FBI and other agencies to try to bring Amy home," he said. "It's obviously still a high priority for our department. We'll pull out all the stops to follow up on any leads."

On Aug. 5, 1989, Amy and her father, Marshall Midden, went up to the family's 140-acre wooded farm in Maple Ridge Township to harvest trees and farm vegetables. About 5 p.m., Midden and Amy were returning home, when he stopped at a Holiday gas station 2 miles away in Osseo, Midden told police. He said he used the bathroom and came out to find the car empty.

Amy's mother, Susan Pagnac, has said in Star Tribune interviews that Amy was prone to seizures, wandering off at times. She also said Amy could've been abducted for prostitution, with someone claiming to spot Amy at a strip club years later and at a bus or train station in 1992.

Police haven't confirmed those details. But the amount of time — more than two decades — that's passed has posed a challenge to the case. There also is no suspect or evidence of a crime.

Time, however, has improved DNA technology. In fact, in 2013, Amy's case was mentioned in an Associated Press article on the BCA's new efforts to use DNA samples to identify human remains statewide. While forensic scientists have been testing DNA for decades, in the last few years, extraction and testing capabilities have advanced, allowing scientists to derive DNA from old remains, even if damaged.

"Law enforcement has changed significantly the last 25 years in the scientific realm," Terlinden said. "We're using some of the best experts nationwide to help with this case."

Just two months after Amy disappeared, Jacob Wetterling was abducted by a masked gunman in St. Joseph, Minn. In 2010, investigators swarmed a farm near the spot where Wetterling disappeared, digging up six truckloads of dirt and ash. Four years later, nothing new has been reported in his case.